Fly Tying Thread Comparison Chart: Choosing Fly Tying Thread

The most common fly tying thread materials today are nylon, polyester and GSP (gel-spun polyethylene).

Nylon emerged in the 1930s as the first synthetic substitute for traditional silk thread. Nylon has approximately 25% stretch, making it forgiving for beginners and ideal for applications that require some elasticity. Created through continuous extrusion, nylon excels at accepting vibrant dyes, resulting in the brightest color selections available. Its moderate stretch helps prevent accidental breakage during tight wraps, though this same characteristic can create slight bulk in delicate patterns.

Polyester offers a different approach to synthetic thread construction. Available in both continuous filament and short-fiber configurations, polyester around 15% stretch provides less elasticity than nylon but more predictable behavior. The amount of stretch is approximately 3 ½% compared to 16% to 24% for polyester and nylon for GSP threads. Polyester's reduced stretch means it will break with less warning under excessive tension, requiring more careful handling. Colors tend to be slightly more muted than nylon, but the material offers excellent durability and consistent performance.

Gel-Spun Polyethylene (GSP) represents the cutting edge of thread technology. some of the other qualities of gel-spun thread that make it a good choice for tying include: it does not absorb water, it floats, it has excellent UV resistance, and it is very supple. gel spun only 3% stretch makes it extremely strong for its diameter, though this strength comes with challenges. GSP's slippery texture requires different handling techniques, and the material will cut through metal after regular use, necessitating ceramic bobbin tips for regular use.

Traditional and Specialty Materials still serve important roles in modern fly tying. Natural silk, cotton, and wool threads offer unique properties for historical patterns and specialized applications. Synthetic options like Kevlar and rayon provide specific characteristics for particular tying challenges, though they remain less common in everyday use.

At J. Stockard we stock the industry's leading thread manufacturers, each offering distinct advantages:

• Danville: Traditional nylon threads with consistent quality and extensive color selection
• UNI: Versatile nylon and polyester options for all-around tying
• Semperfli: Innovative materials including specialized GSP products
• VEEVUS: Danish-engineered threads with superior breaking strength for their size
• Wapsi: Reliable nylon and GSP threads for diverse applications
• Gordon Griffiths: Specialized threads, including ultra-fine options for delicate work

Fly Tying Thread Selection

Thread selection depends on multiple factors: fly size, materials being secured, tying technique, and intended fishing conditions. For delicate dry flies, a fine thread like 14/0 or 70 denier is ideal to prevent bulk. For larger flies, such as streamers or bass bugs, a stronger thread like 210 denier ensures durability without breaking under pressure

Most tyers use nylon or polyester threads for most trout-sized flies and polyester or GSP for larger streamers. For the smallest of flies, tyers are typically using GSP, Nano-silk, taking advantage of GSP's exceptional strength in minimal diameter.

Understanding thread sizing is crucial for selecting the right tool for each pattern. Two measurement systems dominate the fly tying world, each with distinct advantages and applications.

Denier System: Denier is a textile industry convention. A particular thread's denier equals the gram weight of 9,000 meters of thread. Therefore the lighter the thread, the lower the denier and vice versa. This standardized measurement provides consistent, comparable sizing across all manufacturers and materials. Common sizes range from ultra-fine 30 denier for delicate dry flies to robust 280 denier for large streamers and saltwater patterns.

Aught (0) System: Aught (0) size is an older, less accurate definition with the more '0's" indicating finer thread. lower numbers mean thicker threads—so 3/0 is much thicker than 8/0. While less precise than denier measurements, many traditional patterns and tying instructions still reference aught sizes, making familiarity with both systems essential.

• 24/0, 18/0, 16/0, 14/0 = Ultra-fine threads
• 12/0, 10/0, 8/0 = Fine threads
• 6/0 = Medium threads
• 3/0 = Heavy threads

Fly Tying Thread Technical Specifications Chart

To help you make informed decisions, we've compiled detailed specifications for every thread we stock. Our comprehensive comparison chart includes denier ratings, breaking strengths, material composition, and recommended applications. Keep this reference handy at your tying bench for quick thread selection guidance.

Whether you're tying size 24 midges or articulated pike streamers, understanding thread characteristics ensures your flies will perform exactly as intended. The right thread choice enhances both the tying process and the finished fly's effectiveness on the water.